Monitor



FIG. 1 is a front perspective view of a monitor according to our new design;

FIG. 2 is a rear perspective view of the monitor;

FIG. 3 shows a side view of the monitor; and,

FIG. 4 shows a leftside view of the monitor.

The undisclosed bottom view is not a part of the claimed design. 

The ornamental design for a monitor, as shown and described. 